While the structure/function relationships of lens crystallins and their roles in protection of the lens from cataractogenic stresses (e.g., the chaperone-like antiaggregative activity of alpha-crystallin; possible antioxidative function of enzyme/crystallins) remain of great interest to this laboratory, the focus of the work has shifted toward certain noncrystallin proteins of the lens. During the past year, an enzyme has been isolated from the lens, which uses the reducing equivalents of NAD(P)H to inactivate free radical species such as the hydroxyl radical. Partial sequence has been obtained, which indicates a distant relationship to known oxidoreductases; however, at present it appears that the isolated protein is a novel enzyme. Dr. Chuan Qin is pursuing characterization of this enzyme, which we believe may be an important component of the antioxidant defenses of the lenses of primates and certain other species. Dr. P. Vasantha Rao is investigating the role of small GTPases in regulating critical cellular processes in the lens. He has demonstrated for the first time the presence in the lens of Ras, which is involved in regulating cell growth and differentiation, and Rho, which is involved in cytoskeletal organization. These signal transduction molecules are present in both the lens epithelial cells and lens fibers. He has also found GTPase-activating and exchange factors in the lens that are required for activity of the GTPases. There appear to be additional, possibly novel, GTP-binding proteins that are fiber cell specific and may be involved in terminal differentiation of lens fibers. Preliminary studies using human lens epithelial cell cultures and lens organ cultures demonstrate that inhibition of the activity of small GTPases leads to massive morphological changes in lens cells and to opacification of cultured lenses. Thus, these initial studies indicate that, as in other tissues, Ras family GTPases function in the lens as molecular switches regulating critical cellular processes and that dysfunction of these important signal transduction molecules could be involved in cataract development. The group is also involved with other investigators in the LMOD in studies on potential anticataract agents. The hydroxylamine reduction product of the nitroxide Tempol has proven very effective in prevention of cataract in an organ culture system. Studies are currently under way to develop effective means of administration of this agent to live animals so that its efficacy for cataract prevention in vivo can be determined.